This study is to define genetic factors that contribute to loss of bone density and osteoporosis. We will collect blood from affected and unaffected members in three families in which there is a family history of disease.Dna will then be isolated from the blood sample. The dna from each member of the family will then be typed for specific markers that are located on specific chromosomes. We will then compare the inheritance of specific chromosomes with disease phenotype and thereby identify potential genes that contribute to disease phenotype.